Sustained and Transient Contributions to the Rat Dark-Adapted Electroretinogram b-Wave

Abstract EN

The most dominant feature of the electroretinogram, the b-wave, is thought to reflect ON-bipolar cell responses.

However, a number of studies suggest that the b-wave is made up of several components.

We consider the composition of the rat b-wave by subtracting corneal negative components obtained using intravitreal application of pharmacological agents to remove postreceptoral responses.

By analyzing the intensity-response characteristic of the PII across a range of fixed times during and after a light step, we find that the rat isolated PII has 2 components.

The first has fast rise and decay characteristics with a low sensitivity to light.

GABAc-mediated inhibitory pathways enhance this transient-ON component to manifest increased and deceased sensitivity to light at shorter (<160 ms) and longer times, respectively.

The second component has slower temporal characteristics but is more sensitive to light.

GABAc-mediated inhibition enhances this sustained-ON component but has little effect on its sensitivity to light.

After stimulus offset, both transient and sustained components return to baseline, and a long latency sustained positive component becomes apparent.

The light sensitivities of transient-ON and sustained-OFF components are consistent with activity arising from cone ON- and OFF-bipolar cells, whereas the sustained-ON component is likely to arise from rod bipolar cells.